Tire constructions have been suggested for pneumatic tires which are designed to be run without internal pneumatic pressure, other than ambient atmospheric pressure.
For example, tires have been suggested which have special sidewall inserts designed to improve sidewall stiffness, thereby reducing, or inhibiting, the tire's tendency to go flat without internal air pressure. (see, for example, U.S. Pat. No. 5,368,082). Also, tires have been suggested which have additional plies, such as tires having a total of three plies in their sidewalls, to enhance, or substantially maintain, the tire's performance when running without internal air pressure. (see, for example, U.S. Pat. Nos., 5,427,166 and 5,511,599).
For this invention, it is desired to provide a tire with inserts in its sidewall portion(s) which have enhanced stiffness related properties.
In the description of this invention, the term "phr" where used, relates to parts by weight of specified material, or ingredient, per 100 parts by weight rubber, in a rubber based composition. Such term is well known to those having skill in such art.
Such terms as "compound" or "rubber compound" or "rubber composition" are used interchangeably. The term "compounding ingredient" refers to ingredients, usually including the elastomers themselves, that are blended to form a rubber compound. Such terms are well known to those having skill in such art.
In the description of this invention, the viscoelastic properties E' and Tangent (Tan.) delta values art determined by a Rheovibron instrument at 11 hz at a one tenth percent strain. A Rheovibron instrument from the Tmass company is used. It is understood that use of a Rheovibron instrument and such method of measurement of E' and Tan.Delta is understood by one having skill in the art. The E' and Tan.Delta values are to be determined at 60.degree. C.
The term "runflat" tire, where used, relates to a pneumatic tire which is designed to run without internal air pressure, under ambient conditions, for limited periods of time and speeds.